1. Field of the Invention
The present invention relates to a map display apparatus and more particularly to a map display apparatus designed so that all the map data of an area to be displayed is recorded in a map data recording medium and the desired map data for display is read from the map data recording medium to display a map.
2. Description of the Prior Art
Various map display apparatus have been proposed in the past in which a road map is displayed on a display including a CRT or the like to guide the movement of a vehicle by the driver and one such apparatus is so designed that the map data of the whole area subjected to map display is preliminarily recorded in a recording medium such as a magnetic tape, magnetic disc or CD ROM and the map data presently required for display purposes is read from the recorded data thereby displaying a map on a display.
On the other hand, if a road map including the names of various parts on the map such as the names of prefectures, cities, towns, roads and intersections as in a commercially available road map is displayed on the display, the driver finds it impossible to distinguish the desired district or spot on the map while driving and the map becomes a hard-to-see map. Thus, a map display apparatus has been conceived in which a recording medium stores map data comprising map information including only the configuration, e.g., rivers, roads, railways, city streets, principal buildings, etc., and various name information indicating the names of various parts on the map in correspondence to the map information and only the desired name information is displayed on a display.
Then, when recording the map data divided into the map information and the name information, it has been the practice to simply record the map information and the name information in separate areas on the map data recording medium and therefore there are disadvantages that the whole recording medium must be searched in order to read the map data of the district required for map display and that even the mere display of the desired name requires searching of all the name information of the districts including those having no relation to the displayed map. This requires a considerable time for extracting the desired map data.